In the semiconductor production process, for various substrates, for example in order to clean a wafer surface, after the wafer surface is cleansed with a chemical solution, washing is performed using a processing solution such as pure water, and the wafer is dried with an organic solvent such as isopropyl alcohol (hereinafter referred to as IPA). More specifically, the processes includes a process, in which, after the wafer is cleansed with the chemical solution and pure water, the wafer is exposed in an IPA vapor to condense IPA on the wafer surface, thus substituting IPA for the pure water adhering to the wafer, and contaminants such as particles are washed from the wafer surface by running pure water down the wafer surface, and a drying process of vaporizing IPA to dry the wafer surface. In the drying process, if even a small droplet of water remains on the wafer surface, a water mark is formed on the wafer surface, which causes wafer quality to be worsened in the same way as a particle does. Therefore, in the semiconductor production process, it is necessary that such contaminants do not adhere to the wafer. Many methods and apparatus for processing the substrate surface of the wafer, in which measures are taken against contaminants, have been devised and put into practical use. Such methods and apparatus for processing the substrate are disclosed in many patent documents such as Japanese Patent Laid-Open No. 2001-271188 (see FIG. 1 and right column of page 5 to left column of page 6).
The substrate processing device described in Japanese Patent Laid-Open No. 2001-271188 includes one processing tank. The processing tank includes a bottomed box body and a lid. The box body has an open upper region. The opening of the box body is covered with the lid. The opening of the box body is formed to a size such that the many wafers can be supported and accommodated at predetermined intervals and in parallel and vertical orientation. The depth of the box body is formed to such extent that the upper space has an appropriate volume in which it is ensured an inert gas can be supplied when the wafers are dipped into it. The processes including the chemical-solution process, the process of washing out the chemical solution from the wafer surface using pure water, and the drying process of removing the water adhering to and remaining on the wafer surface with mixed substitution of the organic solvent vapor and the inert gas after the washing process is performed in the one processing tank.
When the flow of the inert gas within the processing tank was investigated during the wafer drying process, routes shown in FIG. 9 were observed. FIG. 9 is a sectional view schematically showing the flow of the inert gas within the processing tank. Substrate processing device 1 includes a processing tank 2 with an inner tank 21, an outer tank 22, and a lid 23. The outer tank 22 has a bottomed box shape and an open upper region. The inner tank 21 surrounds the outer periphery in the upper region of the inner tank 21. An openable and closable lid 23 is provided in the upper region of the outer tank. A processing solution discharge hole 212 is made in a bottom region of the inner tank 21. One end of the exhaust pipe 5 is connected to the processing solution discharge hole 212, and the other end of the exhaust pipe 5 is coupled to a vacuum pump or the like. Vapor ejection ports 8 are protruded in the outer tank 22, and the vapor ejection ports 8 are coupled to a vapor supply mechanism 9. Gas jet nozzles 41 are mounted in the upper region of the lid 23, and the gas jet nozzles 41 are connected to a nitrogen gas supply source 7 through piping 4.
In the substrate processing device 1, when the nitrogen gas N2 (drying gas) from the nitrogen gas supply source 7 is jetted from the upper region of the processing tank 2, the jetted nitrogen gas N2 flows downward, and the nitrogen gas N2 is jetted onto an assembly of wafers W′, and the nitrogen gas N2 is exhausted outside the tank from an exhaust pipe 5. At this point, some of the jet gas is exhausted outside the sink 3 through the space between the outer tank 22 and the lid 23. The outside of the sink 3 is at atmospheric pressure. As shown by arrows in FIG. 9, the gas jetted onto the assembly of wafers W′ collides with the bottom wall surface of the inner tank 21 and rises to circulate in the processing tank 2, and then the gas is exhausted from the exhaust pipe 5. The surfaces of the assembly of wafers W′ are dried by the gas directly jetted from the jet nozzles 41 and by the gas circulating the inside of the processing tank 2.